Hydraulic control system for weighting and two-way valve therefor

ABSTRACT

A motion control system for hydraulically operated lifting devices. The system provides for the dynamic weighing of a loaded container by controllably directing hydraulic flow through a bypass chamber of a two-way valve. An analog output signal is generated by a hydraulic pressure transducer fluidly communicating with the two-way valve or by a tensiometer mounted on the arms of the lifting device. The two-way valve further provides a second bypass chamber which receives fluid under gravity from the lift circuit line of the hydraulic cylinder for controllably lowering the lifting device. The pressure transducer or tensiometer generates an analog signal proportionate to the weight being lowered and whereby the hydraulic fluid is returned to the reservoir of the hydraulic system independently and downstream of the main operating valve.

This is a division of application Ser. No. 07/683,078, filed Apr. 10,1991, now U.S. Pat. No. 5,139,101.

BACKGROUND OF THE INVENTION

The present invention is generally directed toward controlling theascent and descent of lifting arms of a hydraulically operated liftingdevice. The invention is more particularly directed toward controllinglifting devices of the type used for refuse collection vehicles. Theinvention is yet more specifically directed toward briefly controllingthe ascent and descent of the lifting arms for dynamic accurate weighingof.

The invention is particularly directed toward a two-way valve for use inbypassing the main operation lifting circuit and main operating valve inorder to control the lifting arms wherein a sensor generates an analogsignal received at an analog/digital converter and a microprocessor thatcalculates the weight.

My presently co-pending application Ser. Nos., 07/488,679, now U.S. Pat.No. 5,065,828; 07/614,871, now U.S. Pat. No. 5,038,876; 07/614,870, nowU.S. Pat. No. 5,064,008; and, 07/614,869, now U.S. Pat. No. 5,065,829,disclose hydraulic control systems useful for refuse vehicles thatprovide for static and dynamic weighing utilizing a bypass circuit thatbypasses the lift circuit of the main hydraulic system. The bypasscircuit allows for a controlled motion through a defined path determinedby proximity switch means. To make the weight calculations the lift armsare, however, have to move controllably downward from one referenceposition to another for both gross and new weighing. While the systemsdisclosed in my previous applications are effective, they are in partlimited by requiring both the gross and tare weights to be calculatedonly when the lifting assembly descends through a certain range. Theinformation in these applications is incorporated herein by reference.

The present invention improves upon my previous inventions in thesenoted pending applications by providing a unique two-way valvearrangement that is cooperative with the main operating valve and thelift circuit of the lifting arms of a hydraulic lifting apparatus, suchas a refuse vehicle. The two-way valve has two separate bypass flowpaths through whereby the gross weight may be calculated dynamicallywhile lifted and the tare weight calculated dynamically while thecontainer descends. A microprocessor captures the full and empty weightsat the same range of arm travel, up and down, due to the operation ofproximity sensing means.

The present invention may utilize a hydraulic transducer as a weightsensor located in a flow chamber of the two-way valve, or alternately atensiometer may be mounted on the lift arms. These weight sensors sendanalog signals in proportion to the pressure or strain, respectivelyexerted thereon to a programmed microprocessor for calculating the grossand tear weights during the time that the lift arms are in apre-determined location relative to a proximity switch. The use of atensiometer, strain gauge or load cell avoids the calibration problemsoften caused by the fluctuating hydraulic fluid temperature levels inhigh pressure lines, when a hydraulic pressure transducer is usedtemperature probes are helpful to send a temperature signal to themicroprocessor, which program will take the temperature level intoaccount in the calculation.

Accordingly, it is a primary goal of the invention to provide for acontrol system for hydraulic lifting devices that operates inconjunction preferably with a tensiometer attached to the arms, and alsowith a hydraulic transducers fluidly communicating with the lift circuitof the hydraulic system, for dynamically weighing full and empty liftedcontainers, respectively.

An important goal of the invention is to make the weight calculation ofthe full load while it is lifted and the empty container as it islowered.

It is a very important goal of the invention to provide for a bypasssystem which taps off from the lift circuit of the lift arms to directfluid to a unique two-way valve for controlling the ascent and descentof the lift assembly, whereby accurate weighing takes place during thecontrolled phase.

It is an allied goal of the invention to provide a bypass circuit incooperation with a two-way valve that is useful for operation witheither a hydraulic transducer weight sensor cooperative directly withthe valve, or a tensiometer/strain gauge weight sensor located on thelifting arms; sending analog weight/proportional signals in both casesbased upon the activation of a proximity switch whereby weighing takesplace at substantially the same position for every load in order toinsure accuracy.

SUMMARY OF THE INVENTION

The invention may be summarized as comprising a bypass flow pathbypassing the lift circuit of a hydraulic system that overrides, ormomentarily acts in place of, the main operating valve whereby flow toor from the hydraulic lifting circuit may be controlled at a rate lessthan during normal operation by the main operating valve. A two-wayvalve is provided having a normally open valve in one chamber and anormally closed valve in another. The normally open valve being closableto re-direct flow from the main valve under pressure from a hydraulicpump to a bypass chamber having a flow control valve. The normallyclosed valve is capable of being open for directing flow from the liftcircuit a second flow control valve for passing the hydraulic fluid backto a hydraulic fluid reservoir tank when the lift arms are descending.The operation of closing the normally open valve and opening thenormally closed valve, respectively, makes different flow paths for thehydraulic fluid than during normal operation of the main operatingvalve, whereby the flow is directed through either of the flow controlvalves, so that the ascent and descent of the lifting arms of the systemare substantially slower and more controlled. During the control phase,accurate readings may be made based upon analog signalling from ahydraulic transducer cooperative with the two-way valve or from atensiometer mounted on the lift arms of the lifting assembly. Both thehydraulic transducer mode and the tensiometer mode yield continuousanalog signals during operation of the hydraulic system but whichreadings are only calculated at the microprocessor during the controlledmovement of the lift arms of the hydraulic system caused by activating aproximity switch which signals the operator to activate the two-wayvalve and thus initiating the weight calculation at the microprocessor.

The invention further includes a method for weighing in a hydraulicallyoperated lift apparatus. The method includes operating a main valve tolift a load to a certain location whereby the operator will activate amomentary switch that closes a normally open valve in a bypass circuitthereby directing the flow through a flow control valve and bypass routein a slow controlled manner. The system also includes activating asignal-generating weight sensing means, i.e. a hydraulic transducer or atensiometer, which output analog signal is received by a microprocessorand is calibrated proportionate to the weight. After the weight has beencaptured by the microprocessor, the normally open valve is re-opened andthe hydraulic fluid flow is redirected back to the lifting circuit tocomplete the lifting of the load as needed.

The method further includes sending analog signals from a hydraulictransducer arranged in the lift circuit which analog signals are sent tothe microprocessor pre-calibrated to calculate loads based uponpressures and wherein the analog signals are calculated only at a pointdetermined by the movement of the lift arms of the lifting apparatus toactivate a proximity switch. Alternately, the method otherwise includessending analog signals from a tensiometer, load cell or strain gaugemounted on the lift arms which also generate calibrated analog signalsin proportion to the strain experienced.

The method further includes the activation of the normally open valve ofthe two-way valve by the operator until the weight has been captured bythe microprocessor whereupon the operator releases a momentary switch todeactivate the normally open valve and return control to the main valve.

Upon dumping the load, the method further includes the step of loweringthe load to a position slightly above the proximity switch whereupon theoperator activates another momentary switch to open the normally closedvalve in the two-way valve to controllably direct fluid flow from thepiston back to the hydraulic fluid reservoir. As the arms move toactivate the proximity switch the microprocessor captures the weight andmakes the calculation. When the calculation is made, the microprocessorwill emit a signal to the operator to alert the operator to release themomentary switch which closes the normally closed valve. The remainderof the descent of the lift arms is made by the operator activating themain valve to lower the arms in the normal way.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a refuse vehicle having a hydraulicallyoperated lift arm assembly, a tensiometer on one of the arms, and also astriker pin and proximity switch for signalling a predetermined locationof the arms for weighing;

FIG. 2 is a broken-away portion of one of the lift arms of the refusevehicle showing mounting pads for attachment of the tensiometer;

FIG. 3 shows the mounting of the tensiometer at the mounting pads asshown in FIG. 2;

FIG. 4 shows an optional arrangement of the mounting pads and thetensiometer wherein the pads are in an upright position and thetensiometer is bolted to the sides of the mounting pads;

FIG. 5 is an elevational view of a conventional operating valve bankshowing a pressurized hydraulic feed line, a return line to a hydraulicfluid reservoir, lift and lower lines and lever operable main valve forthe lift arm assembly as shown in FIG. 1, and a plurality of othertypical lever-action valves for a refuse vehicle for operating a packerblade, the front forks of the lifting apparatus, and a tailgate, andalso a valve for dumping the vehicle body;

FIG. 6 illustrates the combination of the hydraulic control system ofthe invention in cooperation with the valve bank as shown in FIG. 5 andthe rearrangement of the hydraulic lines to be cooperative therewith,including a bypass circuit and two-way valve;

FIG. 7 is a diagrammatic illustration of a lift and lower circuit forthe lifting apparatus of the device operated by a main valve and showinga two-way valve and a bypass system for the controlled weighing systemof the invention;

FIG. 8 shows the direction of hydraulic fluid flowing through hydraulicsystem of FIG. 7 during the normal operation of a main valve to raisethe lift arms;

FIG. 9 illustrates the direction of hydraulic fluid during normaloperation of the main valve to lower the arms for the hydraulic systemas shown in FIG. 7;

FIG. 10 illustrates the direction of hydraulic fluid for weighing thegross load while raising the arms and the bypass flow of the hydraulicfluid; and,

FIG. 11 illustrates the direction of hydraulic fluid through thehydraulic system as shown in FIG. 7 for obtaining the tare weight of thecontainer while lowering the arms in a controlled manner whereby thehydraulic flow returning from the lift circuit is bypassed in acontrolled manner.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1-11, like reference numerals throughout refer to the sameelements.

The invention will be described in connection with a refuse vehicle 10,as shown in FIG. 1, however, it will be understood that it hasapplication to a variety of hydraulically operated lifting devices whereaccurate weighing of the loads is required.

The refuse collection vehicle 10 is a well known type used forcollecting refuse and waste by lifting loaded containers and dumpingthem into a collection bin or hopper 11 mounted on the vehicle frame 12.The operator occupies a cab 13 for operation of the vehicle. A pair oflifting arms 14 pivotally are mounted to the frame 12 at 15 on eitherside of the frame 12 and have a generally downward U-shape as similarlydescribed in my above-referenced co-pending applications Ser. Nos.07/488,679; 07/614,871; 07/614,870; and, 07/614,869. FIG. 1 is a rightside view of the refuse vehicle 10 and the arms 14 and 15 shown havesubstantially mirror images on the left side of the vehicle as would beclear. The arms 14 function to engaged refuse containers at forks 16that are pivotally joined to the arms 14 at 15 and are operable by ahydraulic cylinder assembly 17 to be movable relative to the arms 14 foradjustment and leveling of an engaged container, or the like. The arms14 are pivotable about 15 by means of a main hydraulic cylinder 18 thatis supported at the frame 12 at one end and drivingly attached to thearms 14 at either side of the vehicle 10 at connections 19. Thehydraulic cylinder 18 pulls the arms 14 to pivot at 15. In the disclosedembodiment the hydraulic cylinder 18 pulls against the arms 14 to pivotthem to lift a load but the invention is equally functional in systemswhere a hydraulic cylinder pushes during the lifting phase. At the rearof the vehicle 10, a closure gate 20 is provided and is operated bymeans of a hydraulic cylinder 21. Within the bin 11, a hydraulicallyoperated compaction device may be provided for compacting the load, forexample, a packer blade device that is known in the industry.Additionally, the bin or hopper 11 may be pivotal to dump the load bythe provision of another standard hydraulic cylinder means not shown.

Inside of the cab 13 are found the control valves for the varioushydraulic cylinders generally at 22 and an onboard microprocessor andanalog/digital converter generally at 23 and within easy view of theoperator for monitoring and operating the main hydraulic system and thecontrolled bypass weighing system of the invention, as will be explainedwith reference to the other figures.

In one form of the invention, the means for sending analog signalsproportionate to the weight carried by the arms 14 is provided by atensiometer 24 mounted on the arms 14 as shown in FIG. 1. In anotherform of the invention, a hydraulic transducer would be located tofluidly communicate with the bypass system for sending analog signalsproportionate to the pressure sensed in the lift circuit. The inventionbeing usable in either option or equivalents thereof.

Further shown in FIG. 1 is an activator striker pin 25 which activates aproximity switch 26 sensing the activator striker pin 25 as it comesinto close proximity for purposes of generating a signal to the operatorin the cab 13. The proximity switch will be activated initially uponraising of the arms 14 when a load is lifted and then, following theemptying of the load into the bin 11, the switch is activated once againas the activator striker pin 25 moves back into proximity with theproximity switch 26 on the return path downward.

Turning now to FIGS. 2-4, the more specific details of the mounting ofthe tensiometer 24 are shown. In FIG. 2, a broken away portion of arm 14is illustrated having welded thereon a pair of mounting pads 27. Themounting pads 27 having threaded bores 28. With reference now to FIG. 3,it will be seen that the threaded bores 28 are provided to receive atension cap screw 29 at each bore 28 which passes through flanges 30 ofthe tensiometer 24. Each mounting pad 27 being provided in the disclosedembodiment with pairs of threaded bores 28 whereby to be capable ofmounting tensiometers with different connection spacings at theirflanges 30. When a container or the like is engaged by the forks 16,tension and strain are created on the arm 14 between the mounting pads28 as would be understood. In the disclosed embodiment, the tensiometeris provided to send calibrated analog millivolt signals in proportion tothe tension and strain between the mounting pads 28 as they are pulledaway from each by loading tension on the arm 14. Equivalently suitedstrain gauges or load cell devices also may be used, as would be clearto someone skilled in the art.

With regard to FIG. 4, an alternate mounting arrangement for thetensiometer 24 is provided wherein the mounting pads 27 are weldedvertically, or edgewise, to the arm 14 and the tensiometer 24 isattached to the mounting pads 28 in a horizontal arrangement having thetension cap screws 29 to be horizontally thread engaged with thethreaded bores 28. The invention is thereby useful with a wide varietyof lifting devices having different size lift arms, and with a varietyof tensiometers and equivalent strain gauge and load cells sensingdevices, by allowing a variety of mounting arrangements.

In the disclosed embodiment, the microprocessor 23 is calibrated to theparticular location of the tensiometer 24 on the arms 14 so that theweight calculation is accurate for each weight captured. In this regard,the weighing signal to the microprocessor from the tensiometer 24 isintended to be used in the programmed weight calculation atsubstantially the same reference position or the arms for every loadweighed.

The successful use of the tensiometer 24 is obtained in cooperation witha two-way control valve and bypass system as will be explained next withreference to FIGS. 5-11. It is the major intent of the invention toobtain stable dynamic readings on the way up and on the way down by useof the tensiometer 24 or alternately by use of a hydraulic transducer influid communication with the lift circuit line of hydraulic cylinder 18.

Turning to FIG. 5, a detailed view of a conventional valve bank assembly22'. The assembly 22' shows the conventional arrangement in the cab 13and FIG. 6 shows the modified assembly 22 of the invention. Valveassembly 22' would be mountable within the cab 13 generally at adashboard or panel 31 and support assembly 32. At the left side of FIG.5, one of the lift arms 14 is shown for illustrative purposes. In ausual way, the main valve bank assembly 22' provides a lever operablemain valve 33 for raising and lowering the lift arms 14 by means ofcontrolling the action of hydraulic cylinder 18. Next, is another leveroperable valve 34 for activating a packer blade within the bin 11 of thevehicle 10. Thirdly, a lever operable valve 35 is provided for operationof the fork 16 by activating the hydraulic cylinder 17 therefor. Fourth,a lever operable valve 36 is provided for the operation of the tailgate20 by the hydraulic cylinder 21. The fifth illustrated valve is a leveroperable valve 37 for activating a hydraulic cylinder in connection withtipping the hopper 11 to dump the contents, for example, at a landfill.The valve bank assembly 22' receives hydraulic fluid through line 38that is under pressure from a pump taking fluid from a reservoir in aknown manner (not shown). A return line to the reservoir is shown at 39.

The present invention is cooperative with the operation of the mainvalve 33 for controlling the raising and lowering of the lift arms 14.The valve 33 directs fluid under pressure through a lift circuit line 40to one side of a piston within the hydraulic cylinder 18 to pivot thelift arms 14 upwardly. The valve 33 also communicates with a loweringcircuit line 41 for alternately introducing fluid under pressure to theopposite side of the piston of the hydraulic cylinder 18 to lower thearms 14. The lever operable valve 33 has a standard design and providesfor moving a lever from a neutral position to a lift position to directfluid under pressure through one port while receiving fluid throughanother port for return to the reservoir. When moved into the other orlower position, the fluid flows at the ports reverse and the fluid movesin the opposite direction through each port to introduce fluid underpressure to an opposite side of a cylinder piston and force fluid on theother piston side to return to the reservoir. For aid in understanding,with respect to FIG. 6, the fluid flow would be downwardly in the liftline 40 and upwardly in lowering line 41 when raising the arms 14;oppositely, the flow would be upwardly through the lift line 40 andthrough the lowering line 41 when the arms 14 are lowered. The operationwill be further understood in connection with the discussion of thedirectional flow diagrams of FIGS. 8 and 9.

The modification to the conventional valve assembly 22 is shown in FIG.6 at valve assembly 22. A novel two-way valve 42 is added to thehydraulic system to be cooperative with the valve 33 but does not affectoperation of valves 34-37. The lift line 40 for feeding fluid underpressure to the hydraulic cylinder 18 is re-routed from the valve 33 toconnect instead to the two-way valve 42 as shown. A connector line 43 isadded to tap-off from a port of the main operating valve 33 to connectto the two-way valve 42. A bypass or tap-off line 44 joins the two-wayvalve 42 to the reservoir return line 39 at a juncture 45 located at thereservoir-return side of an outlet 46 of the valve bank assembly 22. Thereturn line 39 remains otherwise in the same connective arrangement asin valve bank assembly 22'. The pressurized feed line 38 remains in thesame position as in assembly 22'. Also, the lowering circuit line 41 formoving the hydraulic cylinder 18 in the lowering direction remainsconnected to valve 33 as in the valve bank assembly 22'.

The schematic views shown in FIGS. 7-11 illustrates the flow of thehydraulic fluid through the valve 33, the two-way valve 42, thehydraulic cylinder 18, and the lines 38, 39, 40 and 41.

FIG. 7 is a schematic illustration of the connection of the new two-wayvalve 42 to the hydraulic system of the vehicle 10, wherein the modifiedvalve bank assembly 22 is shown at rest, i.e. no hydraulic fluid flow.FIGS. 8 and 9 illustrate, respectively, the normal, non-bypass operationof the valve bank assembly 22 for raising and lowering the lift arms 14.FIG. 10 illustrates the hydraulic fluid flow during the lifting of liftarms 14 as controlled by the two-way valve 42 for dynamic weighing ofthe gross weight. FIG. 11 illustrates the hydraulic fluid flow ascontrolled by the two-way valve 42 during the lowering of the arms fordynamic weighing the empty weight of the refuse container.

More specifically with respect to FIGS. 6 and 7, the two-way valve 42 isarranged for bypassing the hydraulic flow to and from the lift circuitline 40 to accomplish the controlled motion for dynamic weighing to bemade. Line 43 taps off from the valve 33 at a port 47 at which the liftline, as shown in FIG. 5, was conventionally connected. At the other endof the valve 33, a port 48 communicates with the lowering circuit line41 as in the conventional valve assembly of FIG. 5. The lever action ofthe valve 33 is capable of directing inlet flow from pressure line 38 toflow either outwardly through 47 or 48, or through neither when kept ina neutral position in a known way.

The two-way valve 42 includes a main, or flow through, chamber 49 accessto which is controlled by a normally open solenoid operated valve 50. Afirst bypass chamber 51 taps off of the chamber 49 to either side of thenormally open valve 50 and when flow is received from line 43 viachamber 49, it is controlled by a flow control valve 52 in bypasschamber 51. The main chamber 49 fluidly communicates with a pressuretransducer 53 and a temperature sensor T. Generally between thetransducer 53 and the connection of the two-way valve 42 to the liftline 40, the two-way valve 42 includes a second bypass chamber 54tapping off from the main chamber 49, flow through which is obtained byoperation of a normally closed solenoid operated valve 55 and controlledby a second flow control valve 56. The bypass chamber 54 communicateswith the tap-off line 44 and thereby the return line 39.

At the top of FIG. 7, the hydraulic cylinder 18 is illustrated, showingin dashed lines, a hydraulically operated piston 57 drivable at the endof a piston rod 58. A lift chamber 59 is at the right side of the pistonand a lowering chamber 60 is to the left of the piston 57, whereby fluidentering through line 40 under pressure will fill the chamber 59 todrive the piston to the left and thereby pivot the arms 14. Conversely,fluid entering the lowering chamber 60 under pressure from line 41 willmove the piston 57 to the right for the lowering of the arms 14.

The normal operation for raising the arms 14 is illustrated in FIG. 8.When a load has been engaged at the forks 16 to be dumped into the bin11, the operator moves the lever of the lever operable main valve 33 ofthe valve bank assembly 22 in a first direction which directs flow frominput line 38 to flow outwardly through port 47. This action in turnopens port 48 to receive fluid from lowering line 41. The hydraulicfluid directed through port 47 is conveyed via the tap-off line 43 tothe two-way valve 42. Because the valve 50 is normally open, fluidfreely flows through the flow through chamber 49 and outwardly of thevalve 42 into the lift circuit line 40, which directs the flow into thehydraulic cylinder 18 at chamber 59. Increased pressure in the chamber59 drives the piston 57 in the leftward direction as noted. Hydraulicfluid in chamber 60 is urged outwardly through line 41 and to the port48 of the valve 33. The fluid is received at the port 48 then directedoutward of the valve 33 into the return line 39 and back to thereservoir. In this regard, the tap-off line 43 and flow through chamber49 do not change the flow rate to lift line 40 in any substantial way.

Turning now to FIG. 9, the opposite of the function depicted in FIG. 8is shown, namely, the lowering of the arms 14 by the normal operation ofthe main valve 33. To lower the arms 14, the lever of the main valve 33is moved in an opposite direction whereby to direct flow from thepressure line 38 to flow outwardly at port 48 into the lowering circuitline 41 for introduction of the hydraulic fluid under pressure into thelowering chamber 60 to force the piston 57 in the opposite direction. Aswould be understood, the port 47 can now receive inward flow wherebyfluid will be forced out of chamber 59 back through the lift circuitline 40, the flow chamber 49 of the valve 42, and return through thetap-off line 43 to the port 47. The returning fluid is directed throughthe valve 33 outwardly through to the return line 39 and back to thereservoir. The views in FIGS. 8 and 9 show reverse flow paths throughthe same conduits for moving the piston 57 leftward or rightward toraise or lower the arms 14. This is the normal operating mode of thevalve assembly 22 which causes the arms to move quickly and createslarge pressure and temperature fluctuations, vibration, shaking, andbouncing, which makes weighing quite difficult and extremely inaccurate.

As a result, the present invention provides the two-way valve 42tapping-off along line 43 and returning through line 44 whereby tocircumvent and obviate the difficulties inherent in dynamic weighing andwhich further allows for the dynamic weighing to occur in one motionupward and a return motion downward. The weighing is achieved withoutrequiring a repetitive lowering through a certain range for both grossand tare weight calculations.

Attention is directed to FIG. 10 which schematically illustrates theflow of hydraulic fluid to the hydraulic cylinder 18 for purposes ofcontrolling and stabilizing the hydraulic fluid pressure to takeaccurate weight measurements. First a refuse container is seized bymaneuvering the forks 16 into supportive engagement therewith. Next, theoperating valve 33 is open so that pressurized flow passes from port 47through line 43, main chamber 49 and lift line 40. As the activatorstriker pin 25 approaches the proximity switch 26, the operatoractivates a momentary switch causing normally open solenoid valve 50 toclose. The valve 50 closes thereby blocking flow through the flowchamber 49 and re-directs the hydraulic flow through the flow controlvalve 52 in the first bypass chamber 51 at a much reduced rate. Thestable flows moves through the bypass chamber 51 and back into the flowchamber 49 downstream of the closed valve 50. The fluid flows past thepressure transducer 53 and temperature probe T. Both of the analogsignals generated by the transducer 53 and temperature probe T aremonitored by an onboard microprocessor having an analog/digitalconverter for eventually computing the weight. The arms 14 pivotbackward and the activator striker pin 27 activates the proximity switch26, which serves as a reference point and the microprocessor then makesthe gross weight calculation during receipt of the analog signals atthat moment from the transducer 53 and probe T for a preset duration ofsoftware program. When the weight is captured, the microprocessor willcause to issue an audible, or visual signal, or the like, to theoperator indicating that the calculation has been made. The operatorreleases the momentary switch to deactivate the valve 50 to return it toits normally open position and allowing the normal flow of hydraulicfluid from line 43 through main chamber 49 and into the lift line 40, asin FIG. 8. Accordingly during the operation of the normally open valve50, a controlled rate of flow is introduced into the lift chamber 59 toevenly and smoothly move the piston 57 and therefore provide stableconditions at the pressure transducer 53 and temperature probe T to makean accurate weighing.

Upon dumping the container into the hopper 11, the operator reverses themain operating valve 33 cause the flow from pressurized line 38 to bedirected outwardly through port 48 thereby pressurizing line 41 andlowering chamber 60, as in FIG. 9. This causes the piston 57 to move inthe rightward direction for lowering the arms 14. The port 47 thenreceives fluid flowing from lower circuit line 40 through the flowchamber 49 of the two-way valve 42 and the tap-off line 43. This returnflow is directed by the valve 33 outwardly to the reservoir return line39. As the activator striker pin 25 of the descending arms 14 approachesthe proximity switch 26 which in the disclosed embodiment would be at adistance of about 4-6 inches, the operator shifts the lever of the mainvalve 33 to the neutral position thereby closing both ports 47 and 48.At this point the operator will have briefly stopped the load.

Attention is directed to FIG. 11, wherein the hydraulic fluid flow forcalculating the tare weight is shown, with the main valve 33 in theneutral position the operator then activates a momentary switch to openthe solenoid-operated normally closed valve 55. When valve 55 is openthe hydraulic fluid from chamber 59 drains by force of gravity backthrough the lift circuit line 40 to the main chamber 54 of the two-wayvalve 42. Because the port 47 is closed at the valve 33 return flowoutwardly from chamber 49 through tap-off line 43 is blocked and theonly path is therefore through the second bypass chamber 54 by virtue ofthe opening of the normally closed valve 55. Flow through the secondbypass chamber takes place in a controlled way created by the secondflow control valve 56 permitting flow at a reduced stable rate comparedto that of the normal flow using only the valve 33. The hydraulic fluidflows back to the return line 44 to enter the reservoir return line 39at the downstream side of the valve bank assembly 22 shown at 46 in FIG.6. The smooth controlled gravity descent of the arms 14 cause stablefluid pressure chamber 49 at the transducer 53 and temperature probe T.The arms 14 move downward until the activator striker rod 25 activatesthe proximity switch 26. A signal then generated from the proximityswitch 26 acts as a reference point whereby the microprocessormomentarily captures the net weight as the arms moving in this referenceposition, which may be a period of about 1/2 second after activating theswitch 26. Upon capturing and making the net weight calculation, avisual or audio signal, or the like, is generated by the microprocessorindicating to the operator that the calculation of the tare weight hasbeen made. The alerting signal and means therefor would be determined bythe microprocessor program and system. Then the operator releases themomentary switch and the normally closed solenoid-operated valve 50closes again. The operator then moves the lever of the valve 33 to thelowering position as in FIG. 9, so that the fluid flows under pressureoutward through port 48 into chamber 60, which urges the piston 57 in amore forceful manner in the opposite direction to lower the arms 14.This action forces fluid in the lift chamber 59 back through the liftcircuit line 40, main chamber 49, and tap-off line 43 to port 47 andthen outwardly of the valve 33 to the reservoir return line 39. Theforks 16 are ultimately returned back to the lowered position shown inFIG. 1 for disengagement with the non-empty refuse container, or thelike.

The onboard microprocessor may be provided with a program forcalculating the total weight dumped into the hopper 11 during theworkday and also for individually calculating loads collected from eachparticular customer. The software program of the microprocessor willtake into account the calibration of the temperature probe T incombination with the simultaneous analog pressure signal of thetransducer 53.

The invention further provides the alternate embodiment for a weightsensor wherein the tensiometer 24 would generate the analog signalreceived by the microprocessor during the momentary period afteractivating the proximity switch at the reference position during liftingand lowering.

Accordingly, the calculations made by the microprocessor and for eitherthe transducer 53 or the tensiometer 24, occur during a controlled phaseof the lifting and lowering of the arms caused by operation of thetwo-way valve 42 and the two bypass chambers 51 and 54, respectively.

It will also be apparent that the flow control valves 52 and 56 mayprovide for different flow rates. Thus individual calibrations forraising and lowering rates can be made and greater accuracy obtained.

It will be understood that the proximity switch 26 would be a commonreference point for calibration of the weight so that the weightcaptured for empty and full containers would be made at the samelocation to provide for accurate calibration. Signals received before orafter the reference position are ignored by the microprocessor in makingthe weight calculation.

The foregoing description of the exemplary embodiment shown in FIGS.1-11 is provided for purposes of explaining the invention, but is notintended to limit the scope and broad range of equivalents of the claimsappended hereto.

What is claimed is:
 1. A flow control system for a hydraulicallyoperated lifting apparatus capable of controlling the ascent and descentof the lifting apparatus at a rate less than the rate provided by a mainhydraulic valve of the system, said flow control system comprising atwo-way valve connected to a port of the main hydraulic valve andproviding a flow through passage therein communicating with a liftcircuit line means of a hydraulic cylinder of the lifting apparatus,said two-way valve including in said flow through chamber a normallyopen valve whereby fluid under pressure can be directed from said portthrough said two-way valve to the lift circuit line means, a bypasscircuit fluidly communicating with said flow through chamber at eitherside of said normally open valve and including therein a flow controlvalve for reducing flow through the two-way valve upon closing saidnormally open valve whereby to direct fluid under pressure at a reducedrate to said lift circuit line means, said two-way valve including asecond bypass chamber fluidly communicating with said flow-throughchamber between said normally open valve and said lift circuit linemeans and having therein a normally closed valve and a second flowcontrol valve, said normally closed valve being openable to direct fluidback from the lift circuit line means through said second bypass chamberat a controlled rate and wherein said second bypass chamber communicatesoutwardly of said two-way valve with a return line means for returninghydraulic fluid to the hydraulic system of the lifting apparatus.
 2. Theflow control system as claimed in claim 1 wherein said main hydraulicvalve is operable to direct fluid through said port for raising thelifting apparatus and to selectively direct flow in an oppositedirection to lower said lifting apparatus, wherein said main hydraulicvalve having a neutral position preventing flow therethrough and saidnormally closed valve is capable of being open when said main hydraulicvalve is in the neutral position to receive said flow back from the liftcircuit line means through said second bypass chamber.